In recent years, an optical device such as a cell phone is structured on which an optical unit for photographing is mounted. In the optical unit, in order to restrain or reduce any disturbance of a photographed image due to a shake in the hand of a user, a technique has been proposed in which an angular velocity sensor, a photo reflector and a shake correction drive mechanism are disposed around a lens and, on the basis of a detection result for a shake by the angular velocity sensor, the shake correction drive mechanism is controlled and the position of the lens is monitored by the photo reflector (see Patent Literature 1).